The focus of this Center is the gamete as a contraceptive target. Remarkable advances have occurred recently in genomics and proteomics, cell biology, fertilization research and drug discovery. These advances have combined to open new possibilities for contraceptive intervention, directed against gametes, that may have been previously imagined but were unattainable. Most of our projects target sperm, though one project proposes a potential egg target. Anti-sperm contraception can block sperm function or sperm development. Our Center's projects include both targets. A major theme of the Center is small molecule inhibitors to block sperm function. Our Center is actively studying sperm plasma membrane proteins that function in sperm-egg interaction and we propose screens for small molecules that inhibit these sperm proteins and thus prevent fertilization. A second theme is to block sperm development. Novel pharmacological strategies to derail the complex process of sperm production are proposed here. All of us who study sperm development are aware of important advances in spermatogenesis and realize that new, feasible contraceptive targets are being identified. Thus, we have proposed an expansion of our target list in spermatogenesis, increasing our scope and chances of developing new products for birth control.